Chain-stitch sewing machine

ABSTRACT

Chain-stitch sewing machine includes: a looper provided under a needle plate and having a thread lead-in port and thread lead-out port, the looper being rotationally driven in synchronism with a sewing operation; a plurality of thread feed ports connecting to different thread supply sources; and a connecting member having a thread passage, the connecting member selectively connecting any one of the plurality of thread feed ports to the thread insertion port of the looper via the thread passage. Threading mechanism passes the sewing thread, fed via the thread feed port connected by the connecting member to the thread insertion port of the looper, into the thread insertion port and causes the sewing thread to be taken out via the inserted thread lead-out port of the looper.

This application is a U.S. National Phase Application of PCT International Application PCT/JP2006/308148 filed on Apr. 18, 2006.

TECHNICAL FIELD

The present invention relates to a chain-stitch sewing machine capable of multi-color, chain-stitch sewing by a single looper selectively using a plurality of sewing threads of different colors and characteristics. More particularly, the present invention relates to a chain-stitch sewing machine suited to perform chain-stitch sewing on a cylindrical sewing workpiece.

BACKGROUND ART

Chain-stitch sewing machines have been known, in which chain-stitch sewing is performed on a sewing workpiece by cooperation between a reciprocatively-driven hook needle and a looper positioned under a needle plate to feed a sewing thread and by rotation of the looper being controlled in synchronism with sewing operation of the hook needle. Also known today are chain-stitch sewing machines of a type which has a single looper per machine head (also called “sewing head”) and in which a plurality of sewing threads of different colors and characteristics are prepared for the single looper; in these chain-stitch sewing machines, chain-stitch sewing with multiple color threads (i.e., multi-color chain-stitch sewing) is performed on a sewing workpiece by selectively inserting any one of the sewing threads through the looper. One example of such chain-stitch sewing machines, capable of multi-color chain-stitch sewing by a single looper selectively using a plurality of sewing threads, is disclosed in Japanese Patent No. 3457040 (hereinafter “Patent Literature 1”) or Japanese Patent Application Laid-open Publication No. 2002-317374 (hereinafter “Patent Literature 2”). In the conventional chain-stitch sewing machine disclosed in Patent Literature 1 or Patent Literature 2, a thread feed mechanism slidable in a horizontal direction is disposed under the looper for selectively supplying any one of a plurality of sewing threads. The plurality of sewing threads are set on the thread feed mechanism in parallel with one another along a sliding direction of the thread feed mechanism. Sewing thread color change (i.e., color thread selection) is effected by sliding the array of the plurality of sewing threads, by means of the thread feed mechanism, so that any desired one of the threads is positioned directly beneath the looper and then passing the sewing thread, positioned directly beneath the looper, through the looper by injection of air.

As noted above, the conventional chain-stitch sewing machines are constructed to effect a sewing thread color change by sliding the array of the plurality of sewing threads by means of the thread feed mechanism that has the plurality of sewing threads set thereon in parallel with one another. Thus, it is difficult to reduce the size of the machines, and there is a need to secure a sliding space (i.e., leeway space for horizontal movement) of a width that is about twice as great as the horizontal width of the array of the plurality of sewing threads. Therefore, the conventional chain-stitch sewing machines of the type, capable of effecting color thread selection, can be applied only to planar-shaped sewing workpieces, although sewing workpieces to be processed by the sewing machines also include cylindrically-shaped sewing workpieces, such as T-shirts and hats. As well known, in order to perform ordinary sewing or embroidering on a cylindrically-shaped sewing workpiece, it is necessary to position a cylindrical rotary hook bead, having a rotary bed provided therein, inside the cylindrically-shaped sewing workpiece. Similarly, in order to perform chain-stitch sewing on a cylindrically-shaped sewing workpiece, it is necessary to position a looper inside the cylindrically-shaped sewing workpiece. However, in the conventional chain-stitch sewing machines, which are capable of effecting a sewing thread color change by passing a desired one of the plurality of loopers through the single looper, it is difficult to reduce the size of the machines and necessary to secure a wide sliding space (leeway space for horizontal movement) because the array of the plurality of sewing threads itself is slid horizontally along the sliding direction of the thread feed mechanism. Therefore, cylindrically-shaped sewing workpieces, on which the conventional chain-stitch sewing machines can perform chain-stitch sewing, are limited to those of relatively great sizes, but also, even for cylindrically-shaped sewing workpieces of great sizes on which the conventional chain-stitch sewing machines can perform chain-stitch sewing, sewable ranges of the workpieces would be extremely limited; consequently, the conventional chain-stitch sewing machines would lack practical utility. Thus, in effect, there has heretofore been no chain-stitch sewing machine suitable for performing multi-color chain-stitch sewing on cylindrically-shaped sewing workpieces.

DISCLOSURE OF THE INVENTION

In view of the foregoing, it is an object of the present invention to provide a chain-stitch sewing machine, of a type having one looper per machine head, which has a compact thread feed mechanism for selectively feeding a desired one of a plurality of sewing threads to the looper to permit sewing with the desired thread. It is another object of the present invention to provide a chain-stitch sewing machine suited for performing chain-stitch sewing on a cylindrically-shaped sewing workpiece using threads of multiple colors.

According to a first aspect of the present invention, there is provided a chain-stitch sewing machine, which comprises: a reciprocatively-driven hook needle; a looper disposed under a needle plate and having a thread lead-in port and thread lead-out port, the looper being rotationally driven in synchronism with a sewing operation; a plurality of thread feed ports connecting to different thread supply sources: a connecting member having a thread passage, the connecting member selectively connecting any one of the plurality of thread feed ports to the thread insertion port of the looper via the thread passage; and a threading mechanism for passing the sewing thread, fed via the thread feed port connected via the connecting member to the thread insertion port of the looper, into the thread insertion port and causing the inserted sewing thread to be taken out via the thread lead-out port of the looper.

According to the first aspect of the present invention, the provision, between the plurality of thread feed ports and the looper, of the connecting member that selectively connects any one of the plurality of thread feed ports to the thread insertion port of the looper via the thread passage can make compact mechanisms for selecting and feeding a thread to the looper. As a consequence, the looper and all of such mechanisms for selectively feeding any one of threads, having different colors and characteristics, to the single looper can be accommodated compactly within a looper base having a cantilevered shape with its one end portion projecting outwardly. Thus, a cylindrically-shaped sewing workpiece can be taken in and out via the one end portion of the looper base, and therefore, there can be provided a chain-stitch sewing machine suited for chain-stitch sewing on cylindrically-shaped sewing workpieces. Further, the construction of the mechanisms for selecting and feeding a thread to the looper can be made compact as compared to the conventional counterparts, and thus, the present invention can advantageously be applied to a sewing machine which performs chain-stitch sewing on planar-shaped sewing workpieces as well as cylindrically-shaped sewing workpieces.

In a preferred embodiment, the connecting member, provided between the plurality of thread feed ports and the looper, is selectively movable to align the inlet of the thread passage with any one of said plurality of thread feed ports. With such a construction that the connecting member is moved without the arrangement or array of the plurality of thread feed ports being moved, it is possible to simplify the construction of the slide mechanism and reduce the size of a movement mechanism; besides, it is possible to eliminate a need for an extra space to secure a movable (e.g., slidable) range of the movement mechanism (because the plurality of thread feed ports themselves are not moved horizontally).

In another preferred embodiment, the plurality of thread feed ports are arranged in a circular configuration, and any one of the plurality of thread feed ports is aligned with the inlet of the thread passage by pivoting movement of the connecting member along the circular configuration. Thus, the mechanism for feeding a sewing thread to the thread insertion port of the looper can be reduced in size. Further, because color thread selection can be effected by the connecting member being moved along the circular configuration instead of being slid horizontally, it is possible to eliminate a need for an extra space to secure a movable (e.g., slidable) range of the movement mechanism. As a result, the present invention can be applied even more advantageously to a sewing machine which performs chain-stitch sewing on cylindrically-shaped sewing workpieces.

According to another aspect of the present invention, there is provided a chain-stitch sewing machine, which comprises: a reciprocatively-driven hook needle; a looper disposed under a needle plate and having a thread lead-in port and thread lead-out port, the looper being rotationally driven in synchronism with a sewing operation; a plurality of thread feed ports arranged in a circular configuration; a selection device for selectively connecting any one of the plurality of thread feed ports to the thread insertion port of the looper; and a threading mechanism for passing a sewing thread, fed via the thread feed port connected via the selection device to the thread insertion port of the looper, into the thread insertion port and causing the inserted sewing thread to be taken out via the thread lead-out port of the looper. Here, the sewing thread taken out via the thread lead-out port is rotated in response to rotation of the looper so that chain-stitch sewing is performed through cooperation between the looper and the hook needle. Because the plurality of thread feed ports are arranged in a circular configuration, even where the arrangement or array of the thread feed ports is to be moved for color thread selection, the array of the thread feed ports can be moved along the circular configuration instead of being slid horizontally, and thus, it is possible to eliminate a need for an extra space to secure a movable (e.g., slidable) range. As a result, the present invention can be applied even more advantageously to a sewing machine which performs chain-stitch sewing on cylindrically-shaped sewing workpieces.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing an outer appearance of a multi-head type chain-stitch sewing machine in accordance with an embodiment of the present invention;

FIG. 2 is a side view of a looper base taken from a right side of the sewing machine of FIG. 1 as the machine is viewed from its front;

FIG. 3 is a sectional side view of the looper base;

FIG. 4 is a top plan view of the looper base;

FIG. 5 is a bottom plan view of the looper base;

FIG. 6 is a front view of the looper base taken from the front of the sewing machine of FIG. 1;

FIG. 7 is a sectional side view, similar to FIG. 3, showing in enlarged scale a distal end portion of the looper base shown in FIG. 3;

FIG. 8 is a perspective view showing, in enlarged scale, a part of an internal construction of the distal end portion of the looper base in the embodiment; and

FIG. 9 is a sectional plan view of an air supply block.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view showing an outer appearance of a multi-head type chain-stitch sewing machine in accordance with an embodiment of the present invention, which is equipped with a plurality of chain-stitch sewing machine heads 3. Reference numeral 1 represents a machine frame, and 2 represents a table that has an ascendable/descendable front table section 2 a. On the front surface of the machine frame 1, there are provided the plurality of (four in the illustrated example) chain-stitch sewing machine heads 3 whose construction is well known per se. Each of the chain-stitch sewing machine heads 3 has a hook needle 4 (see FIG. 7) reciprocatively driven in a vertical direction. Cylindrical looper base (looper section) 5 is disposed under each of the machine heads 3. Base frame (not shown) movable in X and Y directions is disposed on the table 2, and a pair of left and right support arms 6 are provided on the not-shown base frame per machine head 3. Sewing frame 7 having set thereon a cylindrically-shaped sewing workpiece H, such as a body part of a T-shirt, is supported by the pair of left and right support arms 6. The looper base 5 has a shape such that its front distal end portion protrudes into a space, e.g. a cylindrical or rod-like shape, so that it can enter inside a cylindrically-shaped sewing workpiece H set on the sewing frame 7, and it is in the form of a cantilevered support structure having its proximal end portion (i.e., rear end portion) fixed to the machine frame 1.

Internal construction of the looper base 5 will be described in detail. FIG. 2 is a side view of the looper base 5, employed in the instant embodiment, taken from a right side of the sewing machine of FIG. 1 as the machine is viewed from its front, and FIG. 3 is a sectional side view of the looper base 5. In FIGS. 2 and 3, the front distal end portion of the looper base 5 protruding into the space is shown in a left end area of the figures, while the proximal end portion (rear end portion) of the looper base 5 fixed to the machine frame 1 is shown in a right end area of the figures. FIG. 4 is a top plan view of the looper base 5, and FIG. 5 is a bottom plan view of the looper base 5. Further, FIG. 6 is a front view of the looper base 5 taken from the front of the sewing machine of FIG. 1. As clearly seen in FIGS. 2 and 5, a base body member 8 of the looper base 5 is fixed to the machine frame 1 by means of four stud bolts 9. A plurality of covers are provided above and beneath the base body member 8, and the whole of the looper base 5 is covered with these covers. To facilitate understanding, FIGS. 2, 4, 5 and 6 show the looper base 5 with the covers removed (in the figures, the covers are indicated by imaginary lines).

As shown primarily in FIGS. 2, 3, 4, 5, etc., a looper R is provided in a distal end portion (left end portion in FIGS. 2 and 3, or lower end portion in FIGS. 4 and 5) of the base body member 8, and the looper R is rotatably supported by the base body member 8 and a support member 10 fixed beneath the base body member 8 with a predetermined spacing formed between the members 8 and 10. Pulley section Ra is formed on the outer periphery of the looper R. Motor 14 is fixedly provided on a proximal end portion (right end portion in FIGS. 2 and 3, or upper end portion in FIGS. 4 and 5) of the base body member 8, and a driving pulley 15 is fixedly provided on the shaft of the motor 14. Further, a bearing member 13 is provided between the distal end portion and proximal end portion of the base body member 8 and forwardly of a middle point between the distal and proximal end portions. The bearing member 13 rotatably supports an intermediate pulley section 12 having a large-diameter pulley 12 a and small-diameter pulley 12 b vertically spaced from each other with the base body member 8 held therebetween. Timing belt 16 is wound at its opposite end on the pulley section Ra of the looper R and the large-diameter pulley 12 a of the intermediate pulley section 12, while a timing belt 17 is wound at its opposite end on the small-diameter pulley 12 b of the intermediate pulley section 12 and the driving pulley 15 of the motor 14. With such arrangements, as the driving pulley 15 rotates by being driven by the motor 14, the rotation of the driving pulley 15 is transmitted to the small-diameter pulley 12 b via the timing belt 17, so that the large-diameter pulley 12 a fixed to the same shaft as the small-diameter pulley 12 b is rotated. Further, as the large-diameter pulley 12 a rotates, the rotation of the large-diameter pulley 12 a is transmitted via the timing belt 16 to the pulley section Ra. In this way, the looper R can be ultimately rotationally driven by the rotational force transmitted from the motor 14.

FIG. 7 is a sectional side view showing in enlarged scale the distal end portion of the looper base 5 shown in FIG. 3, and FIG. 8 is a perspective view showing, in enlarged scale, a part of the internal construction of the distal end portion of the looper base 5. As clearly seen from FIG. 7, the looper R has a thread-passing hole 11 formed vertically therethrough to allow a sewing thread T to pass through the hole 11. The thread-passing hole 11 is shaped to have a curved intermediate portion as shown, and it is formed in such a manner that the sewing thread T, inserted through a lower-end thread-inserting opening or thread insertion port 11 a, can be led out through an upper-end opening Rb. Namely, the thread-passing hole 11 has the lower-end thread insertion port 11 a formed in a position coinciding with the rotation center of the looper R, the upper-end opening Rb formed in a position offset from the rotation center of the looper R, and the curved intermediate portion. Thread lead-out tube 45 is vertically provided in the upper-end opening Rb, and the upper end of the thread lead-out tube 45 is formed as a thread lead-out opening or port 11 b. The thread lead-out port 11 b leads the sewing thread T out of the hole 11 toward a needle hole 43 a that is formed in a needle plate 43 fixed to a bracket 34 and that permits passage therethrough of the hook needle 4. As well known in the art, the sewing thread T led out through the thread lead-out port 11 b is wound around the hook needle 4 by the looper R being rotationally driven as noted above with the hook needle 4 lowered so that a hook portion at the distal end of the hook needle 4 passes through the needle hole 43 a, and then, chain-stitch sewing is performed by the hook needle 4 being raised so that the hook portion hooks the wound sewing thread T to pull the thread T over the surface of a sewing workpiece. Sewing threads T are paid out from a plurality of thread spools positioned on a thread stand, and any one of the sewing threads T paid out from the plurality of thread spools is selectively supplied to the thread-passing hole 11 (as will be later detailed).

As shown in FIGS. 3, 5, etc., a shaft 18 is rotatably supported via a bearing 19 fixed to the underside of the base body member 8 and a bracket 20 fixed to the underside of the support member 10. Driven gear 21 is fixed to a rear end portion of the shaft 18 and held in meshing engagement with a driving gear 22 located beneath the driven gear 21. The driving gear 22 is fixed to a slide shaft 23 driven to slide in the left-right horizontal direction in response to an instruction given to the chain-stitch sewing machine for changing the sewing thread T to be used. The driving gear 22 and driven gear 21 are each in the form of a spiral gear. Therefore, the shaft 18 is driven to pivot, via the driving gear 22 and driven gear 21, as the slide shaft 23 is driven to slide. As shown in FIGS. 5, 6, 8 etc., a plurality of (nine in the illustrated example) guide tubes 24 are disposed along an imaginary circle about the axis of the shaft 18. In each of the guide tubes 24, one of the sewing threads T paid out from the plurality of thread spools positioned on the thread stand (not shown) can be set by being passed from a rear end portion toward a front end portion of the guide tube 24. Each of the guide tubes 24 has a distal end portion supported by the bracket 20; the bracket 20 has, in corresponding relation to the guide tubes 24, a plurality of thread feed ports that function as exits for the sewing threads T set in the corresponding guide tubes 24. Each of the guide tubes 24 has a rear portion, which is bent so that its rear end is oriented substantially vertically downward. The guide tubes 24 have their respective rear ends to a guide member 26 in a left-right horizontal row, and the guide member 26 is fixed to the machine frame 1; in this way, the sewing threads T paid out from the plurality of thread spools positioned on the not-shown thread stand (thread supply source) disposed in a predetermined area below the guide member 26 are pulled into the respective guide tubes 24. Further, portions located forwardly of the rear bent portions of the guide tubes 24 are supported by a support member 25. With such structural arrangements, the plurality of thread feed ports can be provided in the bracket 20 densely or close to one another (i.e., at intervals smaller than installation intervals of the thread stands), and thus, the thread feed ports can be packed compactly; in addition, the looper base 5 can be suitably positioned inside a cylindrically-shaped sewing workpiece H.

Connecting member 27 is fixed to the distal end of the shaft 18 rotatably supported on the underside of the base body member 8 as noted above. As clearly seen in FIGS. 7 and 8, the connecting member 27 has a single slanted, communicating hole (thread passage) 27 a, and a communicating portion 27 b is provided at the distal or front end of the hole 27 a. The communicating hole (thread passage) 27 a extends obliquely with its distal end (left end in FIG. 7) located on an extension of the axis of the shaft 18 and its rear end (right end in FIG. 7) capable of being positioned to align with the distal end of any one of the guide tubes 24 (more specifically, any one of the thread feed ports of the bracket 20). Thus, the connecting member 27 is caused to pivot, a predetermined angle (pitch) at a time, as the above-mentioned shaft 18 pivots, in response to which the communicating hole (thread passage) 27 a can selectively communicate, one after another, with the individual guide tubes 24 having their distal end portions supported by the bracket 20 so that one thread passage, through which the sewing thread T passes therethrough, can be defined in conjunction with any one of the guide tubes 24.

Air supply block 28 is secured to the underside of the support member 10. As apparent from FIGS. 7 and 8, a nozzle 29 is fixed to the air supply block 28, and the air supply block 28 and connecting member 27 are positioned relative to each other in such a manner that the communicating portion 27 b of the connecting member 27 gets into a rear end portion of the nozzle 29. Connecting tube 30 is fixed to the distal end of the nozzle 29 and has its raised upper end tightly abuts against the thread insertion port 11 a of the looper R. FIG. 9 is a sectional plan view of the air supply block 28. Connector 31 is fixed to the air supply block 28, and a tube 32 extending from an air supply source (not shown) is connected to the connector 31. Thus, air is supplied from the air supply source into the air supply block 28. Once air is supplied to the air supply block 28, the air flows, via an air passage 28 a, into an annular space 28 b formed between a nipple portion 29 a of the nozzle 29 and the air supply block 28 and is swiftly introduced from the outer periphery of the nipple portion 29 a into the connecting tube 30 and then blown out of the thread lead-out port 11 b of the thread-passing hole 11. As a consequence, a negative pressure is produced in the nipple portion 29 a so that a thread-sucking force is produced. Namely, as air is supplied from the air supply source after the shaft 18 is caused to pivot and the communicating hole 27 a of the connecting member 27 connects or communicates with the guide tube 24 having a desired sewing thread T passed therethrough, the desired sewing thread T can be passed through the thread-passing hole 11. In this way, a series of feed passages for the sewing thread T can be formed which extends from the thread stand, through the guide tube 24 (thread feed port of the bracket 20) and communicating hole 27 a of the connecting member 27, to the thread-passing hole 11 of the looper R. With such an air supply block 28, air supply source, connecting tube 30, etc., a threading mechanism is defined which functions to pass a thread through the thread insertion port 11 a of the looper R into the thread-passing hole 11.

As shown in FIG. 4, a movable cutter blade 33 is pivotably supported on the bracket 34 fixed to the upper surface of the base member 8. The movable cutter blade 33 has a connecting arm 33 a that is connected via a connecting plate 35 to a lever 36. The lever 36 is fixed to the upper end of a shaft 37 pivotally supported on the base member 8, and a drive arm 38 is fixed to the lower end of the shaft 37 as shown in FIG. 5. The drive arm 38 is connected at its distal end with a fixation block 40 via a connecting rod 39. The fixation block 40 is fixed to a slide shaft 41 that is driven to slide in the left-right horizontal direction in response to a thread-cutting instruction given to the instant chain-stitch sewing machine. Thus, the movable cutter blade 33 is caused to pivot as the slide shaft 41 is driven to slide. Further, a fixed cutter blade 42 is fixed to a side surface of the bracket 34, and the sewing thread T is cut by cooperation between the fixed cutter blade 42 and the movable cutter blade 33. Namely, during a sewing operation, the movable cutter blade 33 is held in a pivotal position indicated by a solid line in FIG. 4, i.e. in a position where it does not have any influence on the sewing thread T lead out from the looper R. In cutting the sewing thread T, the movable cutter blade 33 is caused to first pivot in the clockwise direction of FIG. 4 to a position such that the sewing thread T can be captured by the fixed cutter blade 42 and then pivot in the counterclockwise direction back to the solid-line pivotal position of FIG. 4 with the sewing thread T captured thereby. During that time, the movable cutter blade 33 and fixed cutter blade 42 engage with each other to cut the sewing thread T. At that time, the looper-side thread end portion of the thus-cut sewing thread T is retained by a not-shown retaining member; such retention of the looper-side thread end portion of the cut sewing thread T will be canceled as the movable cutter blade 33 is caused to pivot a predetermined amount in the clockwise direction.

Beneath the rear ends of the guide tubes 24, a thread-pulling device is provided for pulling the thread end portion of the sewing thread T, having so far been inserted in the looper R (i.e., having so far been involved in a sewing operation), so that the thread end portion is positioned within the guide tube 24. As such a thread-pulling device, there may be employed a pulling-down member, increase means for increasing a pulled-down amount of a thread, etc. as disclosed in the above-discussed No. 2002-317374 publication of the application assigned to the same assignee as the instant application. Because the pulling-down member, increase means, etc. are known, they will not be described here. Of course, the present invention is not limited to the aforementioned.

The following lines describe behavior of the chain-stitch sewing machine of the present invention, constructed in the aforementioned manner, when performing chain-stitch sewing on a cylindrically-shaped sewing workpiece. Sewing threads T of different colors and characteristics, paid out from the plurality of thread spools positioned on the not-shown thread stand are set in advance in the individual guide tubes 24. To start the chain-stitch sewing, first the shaft 18 is caused to pivot so that the communicating hole 27 a of the connecting member 27 is connected with, i.e., brought into communication with, any one of the guide tubes 24 which has a desired sewing thread T set therein. Once air is supplied from the air supply source to the air supply block 28, the desired sewing thread T set in the one guide tube 24 is inserted, by the supplied air, into the thread-passing hole 11 of the looper R and led out through the thread lead-out port 11 b. Then, the movable cutter blade 33 is caused to pivot, just as in cutting of the thread, so as to retain an end portion of the sewing thread T led out through the thread lead-out port 11 b by way of the communicating hole 27 a of the connecting member 27, connecting tube 30 of the air supply block 28 and thread-passing hole 11 of the looper R.

Once the end portion of the sewing thread T is retained in the aforementioned manner, not only the motor 14 is activated to rotate the looper R but also the hook needle 4 of the machine head 3 is moved up and down, in synchronism with which the embroider frame 7 having a cylindrically-shaped sewing workpiece H set thereon is moved in the X/Y direction. In this manner, chain-stitch sewing of a pattern, embroidery and/or the like is performed on the sewing workpiece H.

When the sewing thread T used for the chain-stitch sewing is to be changed to another one, the rotation of the looper R and up-and-down movement of the hook needle 4 is halted, and then the movable cutter blade 33 is caused to pivot first in the clockwise direction and then in the counterclockwise direction to cut the sewing thread T. After cutting of the sewing thread T, the movable cutter blade 33 is caused to pivot a predetermined amount in the clockwise direction to cancel the retention of the looper-side end portion of the sewing thread T. After that, the sewing thread T inserted through the looper R is pulled by the not-shown thread pulling device to position the looper-side end portion of the sewing thread T, having been released from the retention, within the guide tube 24. Then, the shaft 18 is caused to pivot so that the communicating hole 27 a of the connecting member 27, is connected with, i.e. brought into communication with, another one of the guide tubes 24 which has a next, desired sewing thread T set therein, air is supplied to the air supply block 28 to cause the sewing thread T to be passed through the looper R, and then the movable cutter blade 33 is caused to pivot so as to retain an end portion of the sewing thread T inserted through the looper R. Then, in a similar manner to the above-described, not only the looper R is rotated but also the hook needle 4 is moved up and down so that chain-stitch sewing with the desired sewing thread T is performed on the sewing workpiece H. As known in the art, examples of the chain-stitch sewing include chain sewing, loop sewing, etc., and switching can be made among these chain sewing, loop sewing, etc. in response to setting of a desired sewing operation.

As set forth above, the embodiment of the chain-stitch sewing machine of the present invention is constructed to guide a plurality of threads to the neighborhood of the looper R by means of the guide tubes 24 and allow any one of the guide tubes 24 and the thread-passing hole 11 of the looper R to communicate with each other. Thus, the embodiment of the chain-stitch sewing machine can significantly reduce the sizes of component parts located beneath the looper R and thereby construct the looper base 5 into a cylindrical shape of a reduced width. In this way, the looper base 5 can be positioned inside any one of a variety of cylindrically-shaped sewing workpieces H. Further, because it is only necessary to rotate the small-size connecting member 27 when the sewing thread T is to be switched to another, not only the drive source can be reduced in size, but also desired thread color change can be effected at high speed.

The embodiment has been described above in relation to the case where air from the air supply source is supplied only to the air supply block 28 so that a sewing thread T set in the guide tube 24, brought into communication with the thread-passing hole 11 of the looper R, can be inserted through the thread-passing hole 11; however, the present invention is not so limited, and air may also be supplied to the neighborhood of the rear end portion of the guide tube 24 so as to assist movement of the sewing thread T in the guide tube 24.

Note that the aforementioned structure for guiding sewing threads T to the neighborhood of the looper R and allowing any desired one of the sewing threads to be inserted through the single looper R by selectively connecting or communicating the thread insertion port 11 a of the looper R with the end of the guide tube 24 via the connecting member 27 need not necessarily be capable of being positioned inside a cylindrically-shaped sewing workpiece H. Namely, the present invention may also be applied to sewing machines which perform chain-stitch sewing on planar-shaped sewing workpieces.

Further, the guide tubes 24 for guiding sewing threads T to the neighborhood of the looper R and the thread feed ports of the bracket 20 may be arranged, for example, in a linear horizontal configuration or array, rather than in a circular configuration or array about the axis of the shaft 18. Of course, in such a case, the connecting member 27 is driven to linearly move, instead of being driven to rotate, so that the communicating hole 27 a communicates with any one of the guide tubes 24. In such a case too, the present invention can significantly simplify the construction of the slide mechanism and reduce the size of the slide mechanism by moving the connecting member 27 without moving the array of the plurality of thread feed ports; besides, the present invention can eliminate a need for an extra space in order to secure a slidable range of the slide mechanism.

Further, as a modification of the present invention, there may be provided opening/closing-controllable shutters in corresponding relation to the individual thread feed ports of the bracket 20, in both of the cases where the plurality of thread feed ports are arranged in a circular configuration and where the plurality of thread feed ports are arranged in a horizontal configuration; in this case, the connecting member 27 may have a plurality of thread passages provided at its inlet in corresponding relation to the individual thread feed ports, and the plurality of thread passages may be connected to one passage at the outlet of the connecting member 27. With such modified arrangements, the present invention permits color thread selection by opening only the shutter corresponding to a desired color thread without moving the connecting member 27. The shutters corresponding to the thread feed ports may be provided either on the bracket 20 or on the connecting member 27.

As another modification of the present invention, the bracket 20, having the plurality of thread feed ports arranged in a circular configuration, may be caused to pivot along the circular configuration. In such a case too, it is possible to eliminate a need for an extra space to secure the slidable range of the slide mechanism, and thus, the looper base 5 can be significantly reduced in size as a whole so that it can be suited for being positioned inside a cylindrically-shaped sewing workpiece set on the embroidery frame 7.

Further, the guide tubes 24 may be of any desired shape other than a tubular shape, as along as they can guide sewing threads T to the bracket 20.

The embroider frame 7, which is driven in the X/Y direction in accordance with sewing pattern data, may be rotationally driven as known in the field of embroidery sewing on hats etc., instead of being driven in the planar X/Y direction alone. Further, the machine head 3 and looper base 5 may be moved in accordance with a sewing pattern. 

1. A chain-stitch sewing machine comprising: a reciprocatively-driven hook needle; a looper disposed under a needle plate and having a thread lead-in port and thread lead-out port, said looper being rotationally driven in synchronism with a sewing operation; a plurality of thread feed ports connecting to different thread supply sources: a connecting member having a thread passage, said connecting member selectively connecting any one of said plurality of thread feed ports to the thread insertion port of said looper via the thread passage; and a threading mechanism for passing the sewing thread, fed via the thread feed port connected via said connecting member to the thread insertion port of said looper, into the thread insertion port and causing the inserted sewing thread to be taken out via the thread lead-out port of said looper.
 2. A chain-stitch sewing machine as claimed in claim 1 wherein said connecting member is selectively movable to align an inlet of the thread passage with any one of said plurality of thread feed ports.
 3. A chain-stitch sewing machine as claimed in claim 1 wherein said plurality of thread feed ports are arranged in a circular configuration, and any one of said plurality of thread feed ports is aligned with the inlet of the thread passage by pivoting movement of said connecting member along the circular configuration.
 4. A chain-stitch sewing machine as claimed in claim 1 wherein said plurality of thread feed ports are arranged in a linear configuration, and any one of said plurality of thread feed ports is aligned with the inlet of the thread passage by movement of said connecting member along the linear configuration.
 5. A chain-stitch sewing machine as claimed in claim 1 wherein said threading mechanism pushes the sewing thread out to the thread lead-out port by an air jet force.
 6. A chain-stitch sewing machine as claimed in claim 1 wherein said plurality of thread feed ports are provided in a bracket, and which further comprises thread guide means extending from the thread supply sources, corresponding to the thread feed ports, to the bracket.
 7. A chain-stitch sewing machine as claimed in claim 6 wherein said plurality of thread feed ports are densely arranged in the bracket.
 8. A chain-stitch sewing machine as claimed in claim 1 wherein said looper is positioned inside a sewing workpiece.
 9. A chain-stitch sewing machine comprising: a reciprocatively-driven hook needle; a looper disposed under a needle plate and having a thread lead-in port and thread lead-out port, said looper being rotationally driven in synchronism with a sewing operation; a plurality of thread feed ports arranged in a circular configuration; a selection device for selectively connecting any one of said plurality of thread feed ports to the thread insertion port of said looper; and a threading mechanism for passing a sewing thread, fed via the thread feed port connected via said selection device to the thread insertion port of said looper, into the thread insertion port and causing the inserted sewing thread to be taken out via the thread lead-out port of said looper, wherein the sewing thread taken out via the thread lead-out port is rotated in response to rotation of said looper so that chain-stitch sewing is performed through cooperation between said looper and said hook needle. 